bench.

I believe the markings on the front ring are the load data, 2.67 grams of smokeless powder and the bottom line indicates that it's set up for a metal jacketed spitzer.

I have an old German guild Mauser and have done a bit of research on these markings.

"7,7 mm" does refer to the "bore" diameter, but my research indicates that it could be either land or groove diameter, so you will need to slug the bore to be sure.

My guess is you're right and it's .318". My rifle is marked 7,8 m/m and a slug miked out at .323".

I believe that "2,67 g G.B.P." means that the proof load was 2.67 grams of Gewehr Blatz Pulver, which was the nitro proof powder. The crown over "N" is the nitro proof mark.

"St.m.G." means that the rifle was proved for use with a steel jacketed bullet (stahl mantel geschoss). I have seen several rifles with markings that also specify the bullet weight. Mine does that: "12,7 g" or 196 grains.

Not sure about the stylized "K" – Krupp logo, maybe? I have seen barrels marked "Krupp Stahl" meaning Krupp steel.

Perhaps others with more expertise can chime in.

I maybe shooting in the dark here, but a K here buy itself shows (Firma Luch U. Wagner, Shul). Whatever that means and for what it worth?
http://proofhouse.com/cm/ger_ord_codes.htm

GBP stands for Gewehr Blättchen Pulver, small square flakes rifle powder.

SDH,

Would you mind posting some barrel details? Length? Diameter at muzzle? Is the cal. marked on the barrel at all?

Looking forward to seeing the photos once you're ready to post them.

cheers,
- stu